I think there will always be high-volume dive shops that can't offer the same level of service as smaller operations that are more focused on personal service.
In a perfect world, every certified diver would be competent diving autonomously and large customer to divemaster/instructor ratios would be no big deal. Unfortunately, the vast majority of divers dive infrequently and often never developed good skills to begin with. Since this is true, diving with large groups is more likely to result in an inferior experience for experienced divers and more of a safety risk for poor divers, than if they were diving in a smaller group.
Which is not to say that dive operators who take out larger groups are unsafe or unethical, because I don't think that's true. I think it would be better to focus on the objective facts about a dive operation, like DM to customer ratio, rather than individual incidents. Should a certified diver have a runaway ascent? No, and a DM can't always prevent it. If you're diving with a large group, is it more likely that something (even just other divers going through their air quickly) is going to potentially impact your dive? Sure.